copy_to_user,copy_from_user,get_user,put_user函数比较

最新推荐文章于 2025-04-24 14:47:52 发布

原创最新推荐文章于 2025-04-24 14:47:52 发布 · 475 阅读

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本文介绍了Linux内核中用于在用户空间与内核空间之间复制数据的几个关键函数：copy_from_user、copy_to_user、get_user及put_user。这些函数分别用于从用户空间复制数据到内核空间、从内核空间复制数据到用户空间、获取用户空间的简单变量以及将简单值写入用户空间。文章详细解释了每个函数的功能、参数及其返回值。

copy_to_user -- Copy a block of data into user space.
copy_from_user -- Copy a block of data from user space.
get_user -- Get a simple variable from user space.
put_user -- Write a simple value into user space.

copy_from_user

unsigned long copy_from_user (void * to, const void __user * from, unsigned long n);
to: Destination address, in kernel space.
from: Source address, in user space.
n: Number of bytes to copy.

User context only. This function may sleep.
Copy data from user space to kernel space.
Returns number of bytes that could not be copied. On success, this will be zero.
If some data could not be copied, this function will pad the copied data to the requested size using zero bytes.

copy_to_user

unsigned long copy_to_user (void __user * to, const void * from, unsigned long n);
to: Destination address, in user space.
from: Source address, in kernel space.
n: Number of bytes to copy.

User context only. This function may sleep.
Copy data from kernel space to user space.
Returns number of bytes that could not be copied. On success, this will be zero.

put_user

put_user ( x, ptr);
x: Value to copy to user space.
ptr: Destination address, in user space.

User context only. This function may sleep.
This macro copies a single simple value from kernel space to user space. It supports simple types like char and int, but not larger data types like structures or arrays. ptr must have pointer-to-simple-variable type, and x must be assignable to the result of dereferencing ptr.
Returns zero on success, or -EFAULT on error.

get_user

get_user ( x, ptr);
x: Variable to store result.
ptr: Source address, in user space.

User context only. This function may sleep.
This macro copies a single simple variable from user space to kernel space. It supports simple types like char and int, but not larger data types like structures or arrays. ptr must have pointer-to-simple-variable type, and the result of dereferencing ptr must be assignable to x without a cast.
Returns zero on success, or -EFAULT on error. On error, the variable x is set to zero.